At the beginning of the 1950s, the recently-established Deutsche Bundesbahn (DB) utilised approximately 6, 000 three-axle passenger carriages for suburban train and passenger train traffic alone. The general condition of these wooden-structured vehicles which were around 50 years old at the time was correspondingly poor. Therefore, DB compared the costefficiency of a refurbishment of the R5 damaged group in which the old Cars would not be modernised with that of a complete conversion. A substitution with completely new constructions was rejected due to financial constraints. As the average costs for the refurbishment matched or, in some cases, exceeded the calculated 35, 000 DM for the conversion, the decision to convert instead was correspondingly easy. The conversions were allocated to the refurbishment facilities in Neuaubing, Karlsruhe, Ludwigshafen, Limburg and Hannover. As a result, the production of, initially, 1, 230 Cars started on 01.02.1954. These Cars were spread across the C3yg, BC3yg and CPw3yg classes. Whilst also reusing the undercarriages from the most diverse international models, a uniform length of 13, 300 mm over buffers was achieved by means of extension, welding or shortening work. The new, fully-welded car body was initially created as a so-called rib construction. However, this method turned out to be uneconomical in mass production. Therefore, the refurbishing factory in Hannover promptly switched to pre-assembling the individual carriage segments and only welding the walls, porch and roof together at the end. On the now-identical layout with asymmetrical distribution, a 3rd class cabin complete with toilet was always present on the smaller side. In contrast, either a large 2nd class cabin, a 3rd class cabin or a baggage compartment with space for the train conductor was optionally available on the handbrake end. By 1959, approximately 6, 500 3yg conversion Cars had been manufactured and it was impossible to imagine commuter traffic without them during the 1950s and 1960s. In order to improve travelling comfort, two Cars were always permanently coupled as a so-called �3yg pair� with a pre-load of 3 t. Upon the class reform and the omission of the 3rd Car class, the designation of the Cars changed to B3yg, AB3yg and BD3yg.